Sydney  - Seven-time Tour de France champion Lance Armstrong set hearts racing Friday in Adelaide as the clock ticked to his return to competition after a three-year lay-off.

Thousands of cycling fans lined the streets of the south coast city to glimpse the 37-year-old Texan on training rides ahead of Sunday's prologue to the six-day Tour Down Under, beginning Tuesday.

Sunday's twilight race is a criterium on an Adelaide street circuit that is unlikely to give an indication of Armstrong's potential.

Former professional Allan Peiper, manager of the top-ranked Columbia-Highroad Team, expressed amazement at the excitement whipped up by the world's best-known cancer survivor.

"As for the Lance Armstrong factor, I've never seen anything like the coverage he's been getting," Peiper said. "It's fantastic for cycling."

Many are convinced they are about to witness one of the biggest comebacks in sporting history when the first stage race of the ProTour season starts next week.

Helping explain the rising fervour is abundant evidence that Armstrong is serious in his intent to go for further glory in July's Tour de France.

He was impressive on a five-hour training ride Thursday that saw him leave Astana team-mates in his wake when the group attacked the Adelaide hills.

"He's looking in superb shape," Astana manager and former professional cyclist Sean Yates said. "At this stage we haven't a game plan in mind, but let me assure you he doesn't want to look like a mug."

Armstrong, Astana's lead rider for this event, has played down his chances in a race of short, easy stages that favours sprinters rather than those whose advantage is endurance, for which he is legendary.

"I hope to be in the mix. I could be completely wrong - I might be the first guy dropped," Armstrong said at a press conference after arriving in Adelaide. "I've a little bit of insecurity and a little bit of nervousness there, and so that's the reason I've tried to train hard and prepare hard."

The Texan is using the Adelaide event as a springboard for the more arduous Tour of California, which comes up next month.

Witnesses to his training rides have said Armstrong looks to be contending well with the 40-degree heat of the southern hemisphere summer.

"He's not going to leave the Tour Down Under without a bit of a show of what he's got in his legs," said Australia's Matt White, a former Armstrong team-mate. "He's going to light it up, alright."

Cycling pundits are predicting that Armstrong will lie low for the first three stages and make his mark on the hillier final three stages.

"I think Lance will try to prove something on one particular day," top cycling commentator Phil Liggett said. "There's always one stage that proves to be pivotal, but you can never say which one."

Saturday, the penultimate day, is tipped as the pivotal stage.

For the first time in the event's 11 years, riders will have to ascend Willunga Hill twice, and the faithful are predicting yet another Alpe D'Huez-style solo breakaway - which means a nail-biting week of waiting for Armstrong die-hards. (dpa)